Batch download StreamCat files for entire US based on desired table

batch-StreamCat-download.R

#FTP location
ftpdir  <- 'ftp://newftp.epa.gov/EPADataCommons/ORD/NHDPlusLandscapeAttributes/StreamCat/HydroRegions/'
#Desired table (change to name of desired table)
table <- 'PredictedBioCondition'

#Get URL, split returned list, select out only desired tables by name ('table' above)
library(RCurl)
url_list <- getURL(ftpdir, dirlistonly = TRUE)
url_list <- strsplit(url_list, split = '\r\n')[[1]]
url_list <- url_list[grep(table, url_list)]

#Loop through files on FTP, download, and append
for(i in 1:length(url_list)){
  print(i)
  temp <- tempfile()
  download.file(paste0(ftpdir, url_list[i]), temp)
  #replace .zip with .csv in file name
  csv_file <- gsub('.zip', '.csv', url_list[i])
  #read in csv
  tmp_metric <- read.csv(unz(temp, csv_file))
  #Append to final table
  if(i == 1){
    outdf <- tmp_metric
  }else{
    outdf <- rbind(outdf, tmp_metric)
  }
}